Magnetically deflected arc lamp

Abstract

The arc of an alternating current discharge lamp may be magnetically straightened by including a small direct current component to the lamp current. The lamp may then be operated substantially as an alternating current lamp, but with out the need to synchronize the magnetic field with the alternating lamp current. The minor inclusion of the direct current component enables the lamp to be magnetically deflected effectively for arc straightening, optical positioning of the arc, offset positioning from the envelope wall to preserve lamp life, and other useful functions.

What is claimed is:  
     
       1. A method of straightening an arc in an arc discharge lamp comprising the steps of: 
       a) providing an alternating current operating component between a first electrode and a second electrode of an arc discharge lamp to generate an arc extending between the first electrode and the second electrode;  
       b) providing an additional on average direct current operating component between the first electrode and the second electrode of the arc discharge lamp; and  
       c) generating a magnetic field having a component in a direction transverse to the arc extension and through the arc.  
     
     
       2. The method in claim  1 , wherein the arc extends substantially in a horizontal direction. 
     
     
       3. The method in claim  1 , wherein the alternating current has a square wave form. 
     
     
       4. A method of straightening an arc in an arc discharge lamp comprising the steps of: 
       a) providing an operating current with a square form between a first electrode and a second electrode of an arc discharge lamp, the operating current having a positive phase and an negative phase, wherein the duty cycle of the positive phase is greater than the duty cycle of the negative phase to generate an arc with a horizontal extension; and  
       b) providing a magnetic field substantially in the horizontal direction transverse to, and through the arc.  
     
     
       5. An arc discharge lamp and power supply system comprising: 
       a) a light transmissive envelope having a wall defining an enclosed volume;  
       b) a first electrode sealingly penetrating the wall to be in electrical contact with the enclosed volume;  
       c) a second electrode sealingly penetrating the wall to be in electrical contact with the enclosed volume; an innermost tip of the first electrode and an innermost tip of the second electrode defining an approximately horizontal axis therebetween;  
       d) a lamp fill positioned in the enclosed volume;  
       e) a power supply providing  
       i) substantially an alternating current of sufficient voltage and current, operating between the first electrode and the second electrode to sustain an arc discharge; and  
       ii) an on average, direct current operating component between the first electrode and the second electrode of the arc discharge lamp; and  
       f) a magnet positioned near the lamp envelope providing a magnetic field with a magnetic field component substantially in a direction transverse to and through the axis.  
     
     
       6. The lamp system in claim  5 , wherein the magnet is a permanent magnet. 
     
     
       7. The lamp system in claim  5 , wherein the on average direct current component may be varied from one value to another value. 
     
     
       8. The lamp system in claim  6 , wherein the magnet is an electromagnet. 
     
     
       9. The lamp system in claim  7 , wherein the current to the electromagnet may be varied from one value to another value. 
     
     
       10. The lamp system in claim  5 , wherein the alternating current has a square wave form. 
     
     
       11. The lamp system in claim  5 , wherein the direct current component comprises a relative increase in the positive phase duty cycle with respect to the negative phase duty cycle of the alternating current. 
     
     
       12. The lamp system in claim  5 , wherein the direct current component comprises a direct current bias current. 
     
     
       13. An arc discharge lamp and power supply system comprising: 
       a) a light transmissive envelope having a wall defining an enclosed volume;  
       b) a first electrode sealingly penetrating the wall to be in electrical contact with the enclosed volume;  
       c) a second electrode sealingly penetrating the wall to be in electrical contact with the enclosed volume; an innermost tip of the first electrode and an innermost tip of the second electrode defining an approximately horizontal axis therebetween;  
       d) a lamp fill positioned in the enclosed volume;  
       e) a power supply providing  
       i) substantially an alternating current of sufficient voltage and current, operating between the first electrode and the second electrode to sustain an arc discharge; and  
       ii) an on average, direct current operating component between the first electrode and the second electrode of the arc discharge lamp;  
       f) a first magnet positioned near the lamp envelope providing a magnetic field with a magnetic field component substantially in a first direction, transverse to and through the axis; and  
       g) a second magnet positioned near the lamp envelope providing a magnetic field with a magnetic field component substantially in a second direction transverse to and horizontal through the axis, and transverse to the first direction.  
     
     
       14. The lamp system in claim  13 , wherein the first magnet is a permanent magnet and the second magnet is an electromagnet receiving a control current. 
     
     
       15. The lamp system in claim  13 , wherein the first magnet is an electromagnet receiving a first control current, and the second magnet is an electromagnet receiving a second control current.